1. Field of the Invention
The present invention relates to a liquid crystal having a color filter substrate and a manufacturing method thereof.
2. Discussion of the Related Art
A liquid crystal display is a display device in which a liquid crystal layer having an anisotropic dielectric constant is formed between upper and lower substrates, which are transparent insulating substrates, and the intensity of an electric field formed on the liquid crystal material is controlled so that the molecular arrangement of the liquid crystal material changes, thereby controlling the amount of light transmitted to the upper substrate serving as a display surface, resulting in the display of desired images.
A representative example of such an LCD includes a thin-film transistor liquid crystal display (TFT LCD) using a TFT as a switching device.
FIGS. 1 and 2 are block diagrams representing a liquid crystal display according to the related art that illustrate viewing-angle controllable liquid crystal displays operated in a wide viewing angle mode and a narrow viewing angle mode, respectively.
The basic principle of the viewing angle control method as shown in FIGS. 1 and 2 is as follows.
First, a liquid crystal panel with a transverse electric field structure is constructed for image display, another liquid crystal panel for viewing angle control is added to an upper or lower part of the liquid crystal panel, and then the added liquid crystal panel is operated to control wide and narrow viewing angle modes. The liquid crystal panel added for viewing angle control basically has the function of preventing the interference with the wide viewing angle characteristics of the liquid crystal panel displaying images and the function of inducing a narrow viewing angle when security and privacy are required.
In FIGS. 1 and 2, the liquid crystal panel including a first liquid crystal layer 80 is a panel for controlling a viewing angle, while the liquid crystal panel including a second liquid crystal layer 90 is a panel displaying images so as to have a wide viewing angle. If a voltage is not applied to the first liquid crystal layer 80, liquid crystal molecules 81 are arranged in parallel between two substrates 10 and 21, and the original wide viewing angle is sustained, thereby resulting in a wide viewing angle mode. If a voltage is applied to the first liquid crystal layer 80, the liquid crystal molecules 81 are arranged perpendicularly between the two substrates 10 and 21 and the viewing angle decreases, thereby resulting in a narrow viewing angle mode.
Referring to FIGS. 1 and 2, first, second, third, and fourth substrates 10, 21, 22, and 30 are disposed in parallel to each other, and transparent electrodes 60 and 70 are respectively formed on inner surfaces between the first substrate 10 and the second substrate 21 and face each other, and two linear electrodes 40 and 50 are formed in parallel to each other on the top surface of the third substrate 22.
First and second liquid crystal layers 80 and 90 are formed between the first substrate 10 and the second substrate 21 and between the third substrate 22 and the fourth substrate 30, respectively.
The liquid crystal panel including the first and second substrate 10 and 21 and the first liquid crystal layer 80 disposed between the two substrates 10 and 21 is a liquid crystal panel for use in viewing angle control that may control a wide viewing angle and a narrow viewing angle.
When an electric field is not applied, as shown in FIG. 1, the liquid crystal molecules of the first liquid crystal layer 80 are aligned parallel to the first and second substrates 10 and 20. In the wide viewing angle mode as shown in FIG. 1, the liquid crystal molecules 91 of the second liquid crystal layer 90 are aligned in the same direction as above, thus obtaining the same viewing angle as the wide viewing angle of a typical liquid crystal display with a horizontal electric field structure having one liquid crystal panel, and not affecting the other characteristics of the horizontal electric field structure.
Two polarizing plates 11 and 31 for polarizing passing light are attached to outer surfaces of the first substrate 10 and third substrate 30, respectively. The transmission axis direction of the polarizing plates 11 and 31 is disposed to be perpendicular or parallel to the orientation direction of the liquid crystal molecules 81 and 91.
FIG. 2 illustrates a case in which the liquid crystal display of FIG. 1 is used in a narrow viewing angle mode.
When a voltage is applied to two transparent electrodes 70 and 60 to form a vertical electric field between the first and second substrates 10 and 21, the liquid crystal molecules 81 of the first liquid crystal layer 80 are arranged perpendicularly to the two substrates 10 and 21 along the direction of the electric field. At this time, the liquid crystal molecules 82 adjacent to the two substrates 10 and 21 are arranged in parallel to the two substrates 10 and 21 because an alignment force caused by rubbing is larger than the force of the electric field.
In such a narrow viewing angle mode, the liquid crystal molecules 81 arranged perpendicularly to the two substrates 10 and 21 do not affect retardation with respect to light proceeding to the front surface of the two substrates 10 and 21.
However, as linearly polarized light passes through the first liquid crystal layer 80 formed of the liquid crystal molecules 81, the polarization state is changed by retardation. The difference in the ratio of change in polarization state becomes more severe as the light is farther away from the front surface. Thus, the contrast ratio is reduced, resulting in a narrow viewing angle.
That is, the viewing angle of the liquid crystal display is reduced by applying an electric field to the first liquid crystal layer 80 added for the purpose of viewing angle control, thereby narrowing the viewing angle.
In this manner, it is possible to switch between the narrow viewing angle mode and the wide viewing angle mode using one liquid crystal display, so the viewing angle characteristics may be adapted as needed.
However, when the viewing angle characteristics of the liquid crystal display are adjusted by means of such a structure, another liquid crystal panel for controlling a viewing angle is used in addition to the liquid crystal panel for displaying images.
Therefore, the overall thickness of the liquid crystal display is excessively increased, thereby incurring additional costs and manufacturing processes and making it difficult to perform the processes such as rubbing, scribing, substrate assembly, etc.